Fluid compressor



Dec. 10, 1940- B. DICK FLUID COMPRESSOR Filed Aug. 19, 1938 2 Sheets-Sheet 1 K H mm E .m m s O N R$$A-FAAVAAAVAAA M M 2 \WI/////// d 2 I BYg x A RNEY.

Dec. 10, 1940. B. DICK FLUID couraizsson Filed Aug. 19, 1938 2 Sheets-She'et 2 HOE,

INVENTOR.

, BURNS DICK Patented Dee-1o, 1940 UNITED STATES PATENT OFFICE 2,224,125 rwm comansson tion of lielaware Application August 19, 1938, Serial No. 225,708

16 Claims.

My invention-relates to fluid compressors and more particularly to compressors of the compensating typewhich are employed, for example, I

, in fluid-actuated brake systems. 5 These compressors -(commonly referred to as master cylinders) employ a packing cup for sealing the piston and in the form now in use in braking apparatus a porthole places the portion of the cylinder ahead of the piston in communication with a reservoir when the piston isin retracted position, whereby expansion and contraction ofthe fluid in the braking system due to temperature changes will not cause decrease or increase of pressureinthe system. l5 When the piston of thecompressor is initially operated and moved to a point where the forward edge of the cup just passes the forward edge of the compensating porthole, the pressure of the fluid in the cylinder ahead of the piston will begin to increase rapidly and consequently such pressure forces the periphery of the cup exposed to the porthole into the hole since there is no pressure other than the static head acting on the reservoir side of the hole. As the piston is moved e farther forward, this portion of the cup that protrudes into the'hole will be rubbed against the edge of the hole, thereby chafing the cup and under some circumstances cutting it. Since the same portion of the cup passes over the porthole on many successivez protractile and retr-actile strokes of the piston, this chafing or cutting will be increased, thus reducing the length of the cups effective service. i

. It is one of the objects of my invention to provide means whereby the porthole will be closed prior'to movement of the packing cup to a position.where it is opposite: the porthole, thereby trapping a body of the incompressible fluid (em-' ployed in brake system) in the porthole and pre- 40 venting the fluid placed under pressure in the cylinder ahead of the piston from forcing a portion of the packing cupinto the hole as the cup. passes the hole and thus cause undesirable jwearingfaction on the cup. v Another object of my invention is to provide means forclosing a compensating porthole prior to any movement of the piston.

Still another object of my invention isto provide means, controlled by the actuating. member of a compressor piston, for closing the compensating porthole closely adjacent the cylinder prior to movement of the piston in pressure applying direction.

Other objects of my invention will become apparent from the following description taken in 7 ing the compensating porthole; and Figure 5 is a 10 cross-sectional View of a vertical type compensator'showing still another modified construction;

. Referringito Figures 1, 2 and 3 in detail, nu-

meral I indicates the reservoir casing of the master cylinder and 2 the cylinder projecting into 5 the lower end of the reservoir. The forward end of the cylinder is connected by a suitable pipe 3 ,with'the fluid motors 4 for actuating the brake shoes of the'brakes 5 '(two only being shown). Within the cylinder 2 is reciprocable a piston 6 2 provided with a packing cup "I, said piston being normally biased to its inoperative or retracted position against the vstop 8 by means of the spring 9. The cylinder is jormed with a compensating porthole Ill which is positioned just 25.

ahead of the lip of the packing cup when the piston is in its retracted position as shown, thus permitting interchange of fluid between the nor-- tion of the cylinder ahead of the piston and the reservoir and thus compensating for any expan- 30 sion and contraction of the fluid in the braking system. The piston B is provided with holes H to permit fluid to pass the piston and the packing cup on the retractile stroke of the piston to prevent sub-atmospheric pressure from developing 35 in the system, whereby air may be drawn therein.

The piston 6 is actuated by means of-an arm i2 secured to a shaft l3 carried by the reservoir. casing. The shaft is actuated by the pedal l4 positioned on the exterior end thereof. A spring 4 I5 biases the actuating structure to its inoperative position and when in this position, the actuating arm'lZ will abut against the end wall of the reservoir casing, as shown.

In compensating compressors of the type de- 5 scribed the compensating porthole i0 is kept 'as small as possible but for reasons already pointed out the inner edge thereof causes considerable chafing or cutting of the lip of the cup I as the cup is moved forwardly over the open end of the 0 hole. In accordance with my invention, I provide means for closing the compensating porthole closely adjacent the cylinder prior to movement of piston 6, thus preventing fluid under pressure from forcing the lip of the cup into the hole and 55 thereby eliminating or reducing, to a minimum, the chafing and cutting. The'mechanism dis-- closed comprises a conical valve element [6 carried on a levermember H, the forward end of which is formed with downturned portions/18 extending into a groove I9 on the forward end of the cylinder wall 2 to form a fulcrum. The rear end ofthe lever member is bifurcated and the two ends 20 are adapted to cooperate with a pin 2| carried by the arm l2. upon lever member I! tending to bias the lever to a position where the conical valve element l6 will seat against the wall of the porthole llfland close the hole. The spring is interposed between the lever and an abutment 23 carried by a cylindrical member 24 secured to a suitable plug 25 attached to the cover plate 26 of the reservoir casing. v

The pin 2| is so positioned on arm i2 that when this arm is in its normally inoperative position abutting the end of the reservoir casing, it will engage the ends 20 of lever H and positively lift the lever and thus the conical valve element 58 upwardly out of engagement with the edge of the porthole as clearly illustrated in Figure 1. The arm I2 is also so constructed and positioned in the reservoir and so associated with piston 6 that when it is in its normally retracted position; the portion thereof which engages thepiston is spaced from the end of the piston a predetermined distance. This distance is such that when arm I2 is moved to actuate the piston, pin 2! will move to a position where the spring 22 can move lever member ii and the conical valve member in order to close the compensating porthole l0.

In operation, when the brakes are released, the parts will be in the position shown in Figure 1. Movement of the pedal It in a counter-clockwise direction will move arm l2 into engagement with the piston. This lost motion movement of the arm will cause pin 2! to move to such a position that the compensating porthole will be closed by spring 22. Thus it is seen that when the piston is initially'moved by arm E2 to :move the packing cup past the compensating port and apply pressure to the fluid in the cylinder 2 ahead of the piston, no fluid under pressure can flow out through the compensating porthole into. the reservoir as would be the case if the porthole were not closed. The lip of the cup will, therefore, not be forced into the porthole so that it can engage the inner edge of the hole and be chafed or cut. The life ofthe cup will thus be appreciably lengthened. It is also to be noted that the conical valve element closes the porthole at a point near its end that communicates with the cylinder. Thus there is only a very small portion of the porthole which contains fluid under pressure as the piston is moved and since this fluid is under approximately the same pressure as that in the cylinder, the lip of the cup will not be forced in the hole.

- The piston is provided with passages 35 (one only being shown) for permitting the fluid to flow from the rear side of the piston and past the A coil spring 22 acts packing cup to the cylinder during the retractile stroke of the piston.

The piston is actuated by anarm 34 carried by a shaft 36 mounted in the reservoir casing and rotated by means of the pedal 31., The arm 35, when in its inoperative position, abuts the cover 38 of the reservoir casing andis normally biased to this position by spring 39. The arm 35 is connected to piston 3| by a connecting rod 40 which is attached to the arm by a ball and socket joint. The rod is of such length that when arm35 is in its inoperative position against the cover 38 and the piston is against stop 32, a lost motion will be present before arm 35 can actuate the piston.

A compensating porthole 4| extends through the cylinder at a point just ahead of the lip of the packing cup when the piston is in its retracted position in order to permit interchange of fluid between the reservoir and the cylinder. This porthole is controlled by a conical valve element 42 which is carried by a lever 43 fulcrumed at 44 on the forward end of the cylinder. The rear end of the lever is formed with a bent portion 45 which carries a cam surface 86 for engaging a conical surface 41 on the connecting rod 86. The spring is carried by a plug 49 screwed into the side of the reservoir casing.

Initial movement of arm 35 to actuate the" piston til to apply pressure to the fluid in the cylinder will first rnove the connecting rod 40 relative to the piston to take up the lost motion. This will cause the conical surface 47 to move away from the cam surface 56 on the end 45 of the lever and permit the lever to" be moved by spring 63 and cause the conical valve element 32 to close the compensating porthole. The closing of this hole will be accomplished prior to the engagement of connecting rod 30 with the piston to move the piston past the porthole. It is thus seen that the construction described will operate in-the same manner 'as that shown in Figure 1 to close the compensating porthole prior to any movement of the piston in its pressure applying direction.

In the construction shown in Figure 5 the reservoir casing 50 contains the cylinder 5! connected to .the braking system by the pipe 52. Within the cylinder is a piston 53 and packing cup 54, the piston being biased to retracted position against the stop 55 by means of the spring 56. The piston is provided with the usual fluid passages 57 (one only being shown) for permitting fluid to flow past the piston and into the cylinder ahead of the piston uring retractile stroke of the piston. The piston is actuated by arm St secured to shaft 39 mounted in the casing. The shaft is rotated by pedal Eli and spring SI normally biases the pedal and arm to its inoperative position where the arm abuts the cover plate 62 of the reservoir. The arm 58 has secured thereto the connecting rod 63 for actuating pis-' ton 53, there being a lost mction between the connecting rod and the piston when the piston is in its retracted position and the arm is in its normal inoperative position against the cover of the reservoir housing.

The compensating porthole St is positioned ahead of the lip of the packing cup when the packing cup and piston are in their retracted positions. The porthole communicates with a chamber 65 in a web 66 of the reservoir casing and this chamber is in communication with the reservoir through the passage 61 having associated therewith a valve seat 68. Within the a by a projecting portion 15 on the rear end of the cylinder. The forward end of rod 13 is'formed with an inclined surface 16 which cooperates with the cam H on valve stem 10. Aspring I1 is interposed between projection and the shoulder 18 on rod 13 and this spring is of suflicient strength to move valve 69 toclosed position against the action of spring l2. The upper rear end of rod 13 carries an arm 19 which is adapted to be engaged by a shoulder 80 on the connecting rod 63 between arm 58 and the piston. The shoulder 80 is so positioned on rod 63 that when arm 58 isin its normally inoperative position, it will move rod 13 against the action of its spring 11 to a position where spring 12 will be effective to hold valve 69 open.

In operation, when the brakes are inoperative, the parts will be in the position shown in Figure 5. The valve 69 will be unseated' and fluid will be free to pass between a portion of the cylinder ahead of the piston and the reservoir. When arm 58 is moved to apply the brakes and during the time the lost motion between the rod 63 and the piston is being taken up, the rod 13 will be moved by its spring TI. Since this spring -is stronger than spring I2 holding valve 69 open, the inclined.

surface 16 will act on cam II to positively seat valve 69 against seat 68. When the connecting rod 63 picks up the piston 53, fluid will be unable to flow through the compensator porthole from the cylinder to the reservoir. Thus it is seen that as the lip of the packing cup passes the edge of the porthole, there will be no flow of fluid through the hole tending to force the lip of the cup into the hole whereby it will engage the edgeof the hole as it passes over said hole. It is noted that in the construction shown in Figure 5 the valve element 69, when seated, will be held so by the fluid pressure built up in cham- -i5 ber 65; The porthole is also closed at a point close to the cylinder. I

Being aware of the possibility of other modifications in the particular structure herein described without departing from the fundamental principles of my invention, I donot intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is: a

1. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when thepiston is in retracted position for permitting communication between the cylinder and reservoir,

said packing cup being formed with a sealing lip which is capable of being forced into the hole by fluid pressure as the cup is moved past the hole in pressure applying direction, valve means for controlling said porthole, means for actuating the piston and comprising a lost motion connection permitting movement of the actuating means from its inoperative position without movement of the piston, and means operable by said actuating means and prior to movement of the packing cup past the porthole for causing said valve means to close the porthole.

2. In a fluid compressor, a cylinder, a piston said packing cup being formed with a sealing lip which is capable of being forced into the hole by fluid pressure as the cup is moved past the hole in pressure applying direction, valve means for controlling said porthole, means for actuat ing the piston, said means having a lost motion connection with the piston when it is in inoperative position and the piston is in retracted position to thereby permit the actuating means to have a predetermined movement from said inoperative position prior to movement of the piston, and means operable by said actuating means when in inoperative position for causing said valve means to be in open 'position,said last named means permitting said valve to be closed when the actuating means is moved and prior to voir, means comprising a porthole in the cylinder wall and so positioned as to be uncovered by the piston and cup only when the piston is in re--' tracted position for permitting communication between the cylinder and reservoir said packing cup being capable of being forced into the hole by fluid pressure as the cup is moved past the hole by the piston in pressure applying direction,-

valve means for controlling said porthole, a member for actuating said piston, connecting means between the member and the piston and providing a lost motion connection when the piston is in retracted position and the member is in its inoperative position, means operable by said member for controlling said valve means, said last named means being operable to maintain said valve means open when the actuating memher is in inoperative position and inoperable when the actuating member is moved to actuate the piston but prior to taking up the lost motion and moving the piston. i

4. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, said packing cup being formed with a seal-ing lip which is capable of being forced into the hole by fluid pressure as the cup is moved past the hole in pressure applying direction, valve means for controlling said porthole and positioned closely adjacent the wall of the cylinder, means for actuating the piston, said means having a lost motion connection with the piston when it is in inoperative position and the piston is in retracted positiommeans operable by said actuating means when in inoperative position for moving said valve means to open position, and spring-operated means for closing said valve means when the actuating means is moved and prior to movement of the piston and the packing cup.

5. Ina fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and so positioned as to be uncovered by the piston and cup only when the piston is in retracted position for permitting communication by fluid pressure as the cup is moved past the hole by the piston in pressure applying direction,

a valve element for cooperation with the porthole, spring-operated means for closing said valve element, actuating means for the piston and having a lost motion connection with the piston when the actuating means is in its inoperative position and the piston is in its retracted position, and means operable by said actuating means when moved to its inoperative position for holding the valve element inopen position, saidvalve element being closed by its spring when the actuating means is initially moved and prior to taking up the lost motion.

6. In a fluid compressor, a. cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and so positioned as to be uncovered by the piston and cup only when the piston is in retracted position for permitting communication between the'cylinder and reservoir, said. packing cup being capable of being forced into the hole by fluid pressure as the cup is moved past the hole by the piston in pressure applying direction, a valve element for cooperation with the porthole, spring-operated means for closing said valve element, actuating means for the piston and having a lost motion connection with the piston when the actuating means is in' its inoperative position and the piston is in its retracted position, and means operable by said actuating :means when moved to its inoperative position for holding the valve element in open position, said means permitting the spring-operated means to close the valve element when the actuating means is operated'and prior to any movement of the piston.

7. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder-and reservoir, a lever having a portion overlying the porthole, a valve element carried by the lever for cooperation with the porthole, a spring for biasing said lever to a position where the valve element is in closed position, actuating means for the piston, and means operable when the actuating means is in its inoperative position for causing said lever to assume a position where the valve element is inopen position.

8. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing .cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communicat ion between the cylinder and'reservoir,

a valve element for controlling the porthole, a lever for actuating the piston, a connecting rod having a lost motion connection with the piston wnen the piston is in its retracted position and the actuating lever is in inoperative position, and means operable by the connecting rod when moved by the lever to establish the lost motion for holding the valve element in open position.

9. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder between the lever and piston, said connectingrod wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, a valve element for controlling the porthole, a lever for actuating the piston, a connecting rod between the lever and piston, said connecting rod having a lost motion connection with the piston when the piston is in its retracted position and the actuating lever is in inoperative position, means operable by the connecting rod when moved by the lever to establish the lost motion for holding the valve element in open position, and spring-operated means for moving the valve element to closed position when the lever is actuated and prior to movement of the piston.

10. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reser-,

voir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, a lever having a portion overlying the porthole, a valve element carried by the lever for cooperation with the porthole, a spring for biasing said lever to a position where the valve element is in closed position, an actuating lever for the piston, a connecting rod between the actuating lever and the piston, said connecting rod having a lost motion connection with the piston when the piston is in its retracted position and the actuating lever is in its inoperative position, and cooperating means carried by the connecting rod and the valve lever for holding the valve element in open position when the actuating lever is in inoperative position.

11. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising'aporthole in the cylinder is in its retracted position and the actuating lever is in its inoperative position, and cooperating cam means carried by the connecting rod and the valve lever for holding the valve element in open position when the actuating lever is in inoperative position, said cam means permitting the valve lever to be moved by the spring to a position where the valve element will be closed when the actuating lever is operated but prior to any movement of the piston and. packing cup.

12. In a fluid compressor, a cylinder, a piston reciprocable insaid cylinder, a packing cup associated with the head of .the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication betweenthe cylinder and reservoir, a lever having a portion overlying the porthole, a valve elementcarried by the lever for cooperation with the porthole, a spring for bias- '2 ing said lever to a position where the valve element is in closed position, an actuating lever for the piston, said actuating lever having a lost motion connection with the piston when the piston is in-its retracted position and the actuating lever is in its inoperative position, and cooperating means between the actuating lever and the valve lever for holding the valve lever in a position where the valve element is in open position when the actuating lever is in its inoperative position, said last named means permitting the valve element to be closed by the spring when the actuating lever is actuated but prior to any movement of the piston and packing cup.

13. In a fluid compressor, a cylinder, a piston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication betweenthe cylinder and reservoir, a lever having a portion overlying the porthole, a valve element carried by the lever for cooperation with the porthole, a spring for biasing said lever to a position where the valve element is in closed position, an actuating lever for the piston, said actuating lever having a lost motion connection with the piston when the pis- 'reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positi ned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, valve means for controlling the porthole and comprising a movable valve element, cam

49 means for closing the valve element, a spring for operating the cam means, actuating means for the piston and having a lost motion connection with the piston when the piston is in retracted position, and the actuating means is in its inop- 45 erative position, and means for preventing said spring means from operating the cam means when the actuating means is in inoperative position,

15. In a fluid compressor, a cylinder, apiston reciprocable in said cylinder, a packing cup associated with the head of the piston, a fluid'reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the cup when the piston is in retracted position for permitting communication between the cylinder and reservoir, valve means for controlling the porthole and comprising a movable valve element, cam means for closing the valve element, a spring foroperating the cam means, 'a lever for actuating the piston, a connecting rod between the lever and piston, said connecting rod having a lost motion connection with the piston when the piston is in retracted position and the lever is in its inoperative position, and means operable by the connecting rod when the lever is in inoperative position for preventing the spring from operating the cam means.

16. Ina fluid compressor, a cylinder, a piston reoiprocable in said cylinder, a flexible packing member movable with the head of the piston, a fluid reservoir, means comprising a porthole in the cylinder wall and positioned ahead of the packing member when the piston is in retracted position for permitting communication between the cylinder and reservoir, said packing member being capable of having a'portion thereot protruded into the porthole when it is moved past the hole, valve means for closing the porthole whereby fluid is prevented from entering or leaving the cylinder through said hole, means for actuating the piston and having a lost motion connection with the piston when said piston is in retracted position and the actuating means is in inoperative position, and means operable by said actuating means for controlling said valve means, said last named means being operable to maintain said valve means-open when the actuating means is in inoperative position and inoperable to prevent said valve means from being closed when the actuating means is moved to actuate the piston but prior to such movement as to take up the lost motion and bring any portion of the packing member opposite the porthole.

BURNS DICK. 

